mainly different crankshafts or different ignitions (ignition
manufacturer having gone bust).
question at the time: who was stronger manufacturer of bike or
manufactuirer of ignition. The weaker one had to modify.
equally some manufacturer in crisis just used whatever material they
had on the day.

different national versions of motorcycle

very often at least different trade names,
but equally differences to accomodate nationally different
regulations (output restrictions) and importer wishes

customer mistaking type of motorcycle

more frequent that you thing.
sometimes even data in road papers (including year of make) are
wrong. We have seen funny cases.

off roads and no end

here scope for mistake is biggest!nearly 50% of data on bikes supplied to us for identification
are wrong or worthless - a KTM 125 e.g. may be anything.
one can not rely on year of make as this sometimes is only year of
registration (opr re-registration for road use)
people using the bike for competion sometimes hide real type or
modifications made. some say they never got papers with the bike.